My Buggy Will not Idle!!

[sminsta]

Hi all, 

 

I am new to this forum so forgive me if this has been asked already! 

 

I have a HPI Trophy 3.5. So, after installing a 3 piece clutch (abisma did a kit so opted for that for the time being) and the buggy not being ran for some time I decided to give it a little bash in the garden. 

 

Only issue is when cold, the buggy idle's perfectly fine, once it starts to get warm you can physically see the car trying to edge forward and when fully warm and the buggy has been ran around for a little while it doesn't idle at a stand still it constantly wants to move (unless applying the brakes). 

 

The gap is at 1mm or so too! Also when coming off the accelerator it bogs and when it is idling (when warm) sounds very lean although all the needles are almost factory. 

 

I'm so baffled as to what I need to do to ensure it idles correctly. I have read many different threads (not being a member) and now very confused. 

 

Can someone point me in the right direction?! 

[Inferno-Chris]

sounds like you need to have a play with the mixture screws mate, to get things smoother.

try turning the idle down a bit too. might stop it from edging forward

[sminsta]

Do you reckon with some tuning of the high speed and low speed needles it should solve the issue? If I have the trim set dead on 0 or neutral it applies the brakes which isn't something I want it doing ideally as its unnecessary stress on the servo. 

 

There's a little pinging sound from the clutch bell also when it's edging forward only every now and then though. Reckon it could be a clutch issue or should I play around with the mixtures first? 

[Inferno-Chris]

adjust the servo arm, and or, the  2 brake bars, and throttle if need be as well.

what i normally do is let the radio gear zero itself out, and switch the power off, then line everything up mechanical, best i can, and just use 1 or 2 trim clicks to balance things out.
if its either revving, or the brakes are on, and theres no neutral, then youll need to get that adjusted.

tweaking the mixtures, will effect your idle a bit too, so you wanna adjust that as you go, to compensate, for the adjustments.

the clutch, im not sure, check the engagement of the gears, make sure there not too tight, or too loose, you can strip teeth on the gears if the adjustments too far out.
failing that, you might wanna pull the engine out, and inspect the clutch, it might be worn or damaged.

Edited May 22, 2020 by Inferno-Chris

[m4inbrain]

That honestly sounds more like a clutch problem than a mixture problem, though there seems something to be off there too.

 

Have a look at this. 

 

That's my old trophy truggy (don't have it no more), right after i changed the clutch to a three shoe one. The idle is slightly high, but that's where it was happy. Solved it with stiffer springs. 

 

Easiest way to see how your engine is running is simply by looking at your exhaust. No exhaust fumes = lean. Clouds upon clouds or even spitting fuel = rich. There's a balance to be found, you have to see smoke, and of course you have to have an infrared thermometer to check engine temp. 

[sminsta]

14 hours ago, Inferno-Chris said:

adjust the servo arm, and or, the  2 brake bars, and throttle if need be as well.

what i normally do is let the radio gear zero itself out, and switch the power off, then line everything up mechanical, best i can, and just use 1 or 2 trim clicks to balance things out.
if its either revving, or the brakes are on, and theres no neutral, then youll need to get that adjusted.

as far as fueling goes - i havent messed around with enough engine to say, but in my experience, the factory setting is always rich. have a play with the hi speed first, untill its at the point of screaming, and then back it off a bit, so its not running lean, and then tweak the low speed, so your getting a clean pull off the mark, and a clean transition between low and high.

i see so many cars, that dont have the low speed tuned properly, and the car bogs down hard, untill it gets going, and then all of a sudden, goes like a rocket. like an 80's car, with loads of turbo lag. 
it shouldnt be like that, it should pull away clean, and rev smoothly, all the way through the range.

tweaking the mixtures, will effect your idle a bit too, so you wanna adjust that as you go, to compensate, for the adjustments.

the clutch, im not sure, check the engagement of the gears, make sure there not too tight, or too loose, you can strip teeth on the gears if the adjustments too far out.
failing that, you might wanna pull the engine out, and inspect the clutch, it might be worn or damaged.

 

Sweet, I'll take this advice on board and have a play around in the garden (abiding by the rules and all that). 

 

I'll reset everything again and start a fresh. I've had nitro buggies before and never had this issue before, always been fairly straight forward and all idled correctly and tuned nice. Very strange to see this for the first time! 

 

I'm going to playing with real cars today especially and try and finish the job and hopefully, get a video of what it's currently doing and get some pictures of the buggy with how it's all currently set up. 

 

Thanks for the response too! Wasn't expecting anyone to reply to quickly  

[sminsta]

13 hours ago, m4inbrain said:

That honestly sounds more like a clutch problem than a mixture problem, though there seems something to be off there too.

 

Have a look at this. 

 

That's my old trophy truggy (don't have it no more), right after i changed the clutch to a three shoe one. The idle is slightly high, but that's where it was happy. Solved it with stiffer springs. 

 

Easiest way to see how your engine is running is simply by looking at your exhaust. No exhaust fumes = lean. Clouds upon clouds or even spitting fuel = rich. There's a balance to be found, you have to see smoke, and of course you have to have an infrared thermometer to check engine temp. 

 

Ah yes that's exactly what mines is doing. Noticed you are having to stop the buggy from rolling and the stiffer springs that you used solved the buggy moving on idle? 

 

Yeah I get plenty smoke at the moment as I purposely left it rich as the engine is fairly new (break in is done) just don't wanna start making it scream straight away. 

 

Again, thanks for the response! I'll take everything on board and have a play with some images and videos to follow. 

[m4inbrain]

Yeah, it'd just run away if i didn't apply brakes or stop it otherwise. Well, not really run, but trod or something. And yes, stiffer springs solved it. You could, if your buggy is happy with it, adjust the idle down, that will stop it too. I'm pretty sure you know, but to make sure: too soft springs basically means that on idle the engine spins already fast enough to throw the shoes outwards. Stiffer springs (or lower RPM) keep the arms in longer, preventing engagement at idle (gotta experiment a little there to find the sweet spot - too stiff a spring, and it won't move on low throttle either, and engage at like 25% of the RPM range. But that's trial and error, really. 

 

I've always run my nitros on the rich side, i'm not racing them so might as well keep them happy. 

[sminsta]

Just now, m4inbrain said:

Yeah, it'd just run away if i didn't apply brakes or stop it otherwise. Well, not really run, but trod or something. And yes, stiffer springs solved it. You could, if your buggy is happy with it, adjust the idle down, that will stop it too. I'm pretty sure you know, but to make sure: too soft springs basically means that on idle the engine spins already fast enough to throw the shoes outwards. Stiffer springs (or lower RPM) keep the arms in longer, preventing engagement at idle (gotta experiment a little there to find the sweet spot - too stiff a spring, and it won't move on low throttle either, and engage at like 25% of the RPM range. But that's trial and error, really. 

 

I've always run my nitros on the rich side, i'm not racing them so might as well keep them happy. 

 

Yeah that's it, my buggy itsn't really a race buggy like the mp9 or the mp10 so I keep mine slightly rich too! 

 

The spring in there at the moment are a medium spring, so maybe a stiffer spring will solve it like yours. This is the only paint with nitro haha lots of tinkering but the rewards are endless. I'll have a play around probably tomorrow or during the week as I plan on rebuilding the diffs hopefully with an update. I'll try and post up images and videos as I said of it currently and after the rebuild etc and new spring during the week a comparison if it's not solved 

[m4inbrain]

Yeah same. 

 

I'm pretty certain a stiffer spring (or lower idle, as mentioned, if possible) will solve it. 

[sminsta]

Sorry for the lack of response, I got a bit carried away with making some carbon shock towers and centre diff plate! 

 

I took the clutch off yesterday to install new springs (which don't fit, great!) But I have found that the springs were also rubbing on the inside of the clutch bell although they were installed as they should have. 

 

I have ordered a fastrax aluminium clutch shoe and spring set for tomorrow! 

 

I may even try and change the orientation of the shoes so that they engage at a higher RPM. Looking at the wear I would have thought these are engaging way to soon? 

[sminsta]

So after trying to have a bash today and installing the new clutch and 1.1mm stiff springs this is the outcome. Even more baffled to say the least, this time the buggy ran away with itself and adjusting the throttle trim on my controller makes it die. It is running very rich as said previously, I've tried to lean it out a little but no real changes. 

 

I may try switching the shoes around tomorrow and see what happens but this is becoming very frustrating

 

 

[sminsta]

So after some tinkering I got the below result! Engine pings and then settles after very minimal throttle. I know the air filter is off that's only because I was setting the idle gap and was only ran for the duration of this video. 

 

The second video is after it was warm and it still doesn't idle. I can only assume this is clutch related even though I've tried everything to do with that now. It sounds lean but setting are all rich. Clutching at straws now lol, I may have to take it to a shop if I can't figure it out and pay them to sort it. 

 

 

 

[Stormbringer]

Hi

with the air filter off and brakes applied lightly there should be about a 1mm gap when you look down where air filter goes

it sounds as if your using throttle trim to adjust idle ?

theres a little screw that adjusts the gap on carb slide and you adjust that to stop it conking out when you brake

[sminsta]

16 hours ago, Stormbringer said:

Hi

with the air filter off and brakes applied lightly there should be about a 1mm gap when you look down where air filter goes

it sounds as if your using throttle trim to adjust idle ?

theres a little screw that adjusts the gap on carb slide and you adjust that to stop it conking out when you brake

 

Hi, I managed to get it to idle yesterday, possibly a little high but seems to be happy! I reset all the needles to factory and richened the LSN slightly more and backed off the idle needle even further. Hopefully it stays happy now, just needs a tune. 

 

Although it bogs under acceleration and cuts out from time to time I'm going to have a play around either during the week or over the weekend. 

 

 

[babylon]

2 hours ago, sminsta said:

 

Hi, I managed to get it to idle yesterday, possibly a little high but seems to be happy! I reset all the needles to factory and richened the LSN slightly more and backed off the idle needle even further. Hopefully it stays happy now, just needs a tune. 

 

Although it bogs under acceleration and cuts out from time to time I'm going to have a play around either during the week or over the weekend. 

 

 

 

You can't look at a nitro like a real car or a 1/5 petrol, If anything, That is a low tick over, Don't forget that at full tilt these things are running between 25 and 30 odd thousand RPM.

To go from  low tick over to full chat in the blink of an eye takes a lot of fuel and air, It's fine  to get the tick over to the speed that the clutch just bites and then just back off a bit. It may sound too fast,  But that's how Nitro engines work.

 This is a good 8 minute watch